Heretofore, the hose used to transport fuel in an automobile has been an ordinary rubber hose, for example NBR•PVC (blend of acrylonitrile butadiene rubber and poly(vinyl chloride) with good vibration absorbency and ease of attachment. This hose has, at present, a gasoline impermeability which satisfies government regulations but automotive fuel permeability regulations are becoming stricter from the perspective of global environmental conservation in recent years, and it is anticipated that these regulations will be increasingly stringent in the future.
In order to satisfy past fuel impermeability, requirements a configuration was used in which a laminated layer of a hard resin possessing impermeability to fuel was formed on the inner surface of a hose body to function as a fuel permeability barrier layer comprising an elastic body.
However, because a resin layer possessing fuel impermeability has the material properties of a hard layer, where the laminated layer formed on the inner surface reaches to the end of the hose body shaft and a rigid companion pipe such as a metal pipe is inserted directly to impact the inner surface, if there is inadequate sealability between the companion pipe and the fuel transport hose or more specifically the resin layer on the inner surface, or if a strong force is necessary when inserting the companion pipe into the opening at the end of the hose shaft deterioration of the hose body and other problems may arise.
Because of this, a connecting structure has been suggested previously as is described in Japanese Unexamined Patent Application Publication (Kokai) No. H8-294979. corresponding to FIG. 5(A).
The fuel supply hose 200 of FIG. 5A (referred to hereafter simply as a hose) includes a rubber hose body 202, and a hard resin layer 204 formed as a laminated layer on the inner surface of the hose body 202 to function as a permeation barrier layer possessing fuel impermeability. The resin layer 204 is laminated over the entire inner surface of the hose body 202.
In this connecting structure, as shown in FIG. 5(A), the inner surface of resin layer 204 is provided with rubber seal 206 possessing fuel impermeability at an end part 212 which is connected to a rigid companion pipe 208 (e.g., as shown in FIG. 5B) when the rigid companion pipe 208 is inserted into resin layer 204 in contact with rubber seal 206, so that the two are fitted together.
With this connecting structure, there is relatively good sealability when companion pipe 208 is directly inserted against resin layer 204.
However, even with rubber seal 206 positioned in between the companion pipe 208 and the end part 212, a strong force is necessary when inserting companion pipe 208 into resin layer 204 because the structure requires the insertion of companion pipe 208 to resin layer 204, and a problem with workability can still arise during the hose connection.
Another connecting structure is described in Japanese Unexamined Patent Application Publication (Kokai) No. 2002-54779 which ameliorates some of the above problems.
Concrete examples of this structure are shown in FIGS. 5(B) and (C).
In the connecting structure shown in FIG. 5(B), resin layer 204 is not formed on end part 212 of hose body 202 leaving the end part 212 completely exposed and causing the inner surface of hose body 202 to make elastic contact directly with the outer surface of companion pipe 208.
In addition a ring-shaped recess 214 is formed in the end part 212 at the inner surface thereof in the vicinity of leading edge 205 of resin layer 204 so that fuel from the part of the interior will not permeate to the exterior of hose body 202, and a fuel-impermeable elastic sealing material 216 is inserted into the recess 214 so that the companion pipe 208 can make contact with the inner surface of elastic sealing material 216 when installing the companion pipe 208.
The elastic sealing material 216 is contained internal of the recess 214 as more clearly shown in FIG. 5(C).
A ring-shaped protuberance 210 is also formed at the insertion end of the companion pipe 208 in the radial direction outwardly from the leading edge of the insertion end of the companion pipe 208. The protuberance 210 is intended to exert elastic compression in the radial direction outwardly against elastic sealing material 216 as it penetrates the interior.
Furthermore, the extent of insertion adjacent to the leading edge of companion pipe 208 along the axial direction at the inner surface of hose 200 is regulated by protruding part 218 formed in the downward direction in the Figure, in other words in the radial direction inwards.
A clamping member 220 is placed over the end part 212 of hose body 202 to clamp the outer surface of the hose body to the companion pipe 208.
The clamping member 220 includes a belt-shaped tightening member 222 and a tightening mechanism 224.
In this connecting structure, since resin layer 204 is not formed on the inner surface of end part 212 of hose body 202, when companion pipe 208 is inserted inward through the opening of the end of the shaft of hose 200, it is possible to carry out the insertion easily with little force compared with the connecting structure shown in FIG. 5(A).
Moreover, because of the configuration in which the inner surface of elastic hose body 202 at end part 212 is directly in contact with the outer surface of companion pipe 208, it is possible to achieve a good seal for fitting hose 200 together with companion pipe 208.
Naturally, since the resin layer 204 is formed on the inner surface of hose body 202 but not on the end part 212 of the hose body 202 a concern arises that fuel on the inside will be able to permeate through hose body 202 to the exterior.
Consequently, impermeable elastic sealing material 216 is provided between the leading edge of companion pipe 208 and hose 200, which will prevent the fuel on the inside from reaching end part 212 between the outer surface of companion pipe 208 and the inner surface of hose 200.
From this it is possible to satisfactorily prevent the fuel on the inside from permeating to the exterior through to end part 212.
However, with this hose connecting structure, when companion pipe 208 is inserted inward through the opening at the end of the shaft of hose 200, protuberance 210 in the radial direction outwards must be inserted past leading edge 205 of hard resin layer 204 on the left side in the Figure, and significant resistance will be encountered in doing so.
Accordingly, even in this connecting structure, there is still room for further improvement in the workability when inserting companion pipe 208 and consequently in the workability of the connection to the hose.
Several examples of fuel transport hoses were explained above, but the difficulties in preventing the permeation of the transported fluid are shared in common by connecting structures for hoses that have laminated layers formed from resin layers that possess impermeability on the inner surface of an elastic hose body.